Patent GB-1361294-A (GB)
Title: Electromagnetic linear motion divice
IPC: H02K35/04
Filed: 1971-07-16
Abstract: 1361294 Linear motors H KOIKE 16 July 1971 33450/71 Heading H2A A linear actuator or generator comprises a field magnet having inner and outer pole-pieces defining an elongated air gap in which a hollow core carrying a coil is movable longitudinally against a spring biasing it to a central position, the core being supported transversely by spaced bearings. As shown in Fig. 1, the inner polepiece 22 is connected to one pole of a permanent magnet 21 to the other pole of which is connected a cylindrical outer pole-piece 23. A single spring 32 stabilizes the coil 26 and core 25 longitudinally in the position shown and the core is engaged by pairs of roller bearings 30, 30<SP>1</SP>, carried by an outer support 27 and positioned at 120 degrees intervals around the core. Alternatively the bearings may be located at spaced points on a spiral curve around the core. The pole-pieces 22, 23 and magnet 21 may be extended as shown in Fig. 6 so that the core can be engaged at opposite ends by springs 35, 35<SP>1</SP>, the support 27 carrying the roller bearings 30. 30<SP>1</SP> being in this case centrally located. The springs may be located outside the device as shown at 46, 46<SP>1</SP> in Fig. 7 and coupled to the core 25 by rods 43, 43<SP>1</SP> and plates 45, 45<SP>1</SP> which may be used to conduct current to the coil 26. In this arrangement, the permanent magnet 21 may be replaced by a ring-shaped magnet (51), Fig. 8 (not shown), inserted in the outer pole-piece 38. Fig. 9 shows another embodiment having such a ring-shaped magnet 53 and in which the coil 60 and its support 59 are carried by a plurality of rods 61 engaged by the bearings 62, 62<SP>1</SP> and connected at their outer ends externally of the device to plates 69, 69<SP>1</SP> slidable on the outer parts 67, 67<SP>1</SP> respectively of telescopic end members 65, 65<SP>1</SP> which are drawn towards each other by a tension spring 68 extending through a central bore 55a. Thus, movement of the coil to the right, for example, causes plate 69<SP>1</SP> to expand the member 65<SP>1</SP> whilst the plate 69 slides over the member 65. As shown, this embodiment has a circular cross-section but it may have alternatively a rectangular cross-section, Fig. 13 (not shown). Also, the bearings 62, 62<SP>1</SP> may be carried by the inner pole-piece 55, Fig. 14 (not shown) instead of the outer one. Fig. 15 shows a further embodiment which is generally similar to that shown in Fig. 9 except that the inner pole-piece 74 carries at its ends pairs of rectangular permanent magnets 72, 72<SP>1</SP> and 73, 73<SP>1</SP> the outer faces of which support a pair of outer polepieces 75, 75<SP>1</SP> thus forming a pair of elongated air gaps 76, 76<SP>1</SP> in which the coil 78 and its support are supported by a pair of rods 83, (83<SP>1</SP>) located in a plane at right angles to that of the pole-pieces 75, 75<SP>1</SP>. The permanent magnets may be replaced by a pair of stationary magnetizing coils (88, 88<SP>1</SP>), Fig. 17 (not shown), which embrace the ends of the inner pole-piece and are connected either in series or in parallel. In either case they may be connected in parallel with the moving coil (90), the stroke of which may be adjusted by a rheostat in series therewith.